Vitamin D May Ward Off Prostate Cancer
Getting a little sunshine may be one
way for men to cut their risk of prostate cancer. A large study
presented at a cancer conference Thursday found that men with
higher levels vitamin D in their blood were half as likely to
develop aggressive forms of the disease than those with lower
Doctors are not ready to recommend
the "sunshine vitamin" without more study, but many see little
harm in getting the 15 minutes a day that the body needs to make
enough of this nutrient.
"When you were little and your
mother said, `Go outside and play,' it wasn't just to get you
out of her hair," but may have been instinctive advice about something
good for health, said Dr. Eric Klein, a prostate cancer specialist
from the Cleveland Clinic.
He had no role in the research,
which involved nearly 15,000 men in the Physicians' Health Study
at Brigham and Women's Hospital and Harvard Medical School in
Boston. Five years ago, this study found that men who consumed
a lot of calcium had modestly higher rates of prostate cancer.
The new findings fit with that
notion, because too much calcium lowers vitamin D, and are especially
believable because researchers got them by measuring blood samples
rather than relying on what men said they ate an imprecision
that has hurt past studies of food and cancer risk.
Blood samples were taken in 1982,
when the study began. Eighteen years later, 1,082 of the men had
developed prostate cancer. Their levels of two common forms of
vitamin D in the stored blood samples were compared with those
of 1,701 men in the study who did not get cancer.
Levels of one or the other vitamin
D derivative did not make much difference in prostate cancer risk.
However, men with higher levels of both had roughly half the risk
of developing aggressive tumors the kind most likely to
kill than men with lower levels, said Dr. Haojie Li, who
led the study.
That is in keeping with what previous
studies have shown about prostate cancer, Klein noted.
Men in northern latitudes have
higher cancer death rates, and vitamin D levels are lower in older
men, who are most prone to prostate cancer.
Melanin, which gives skin its color,
blocks ultraviolet light that spurs vitamin D production. Blacks,
who have a lot of melanin, also have the highest rates of prostate
Experiments also suggest vitamin
D inhibits cell growth. "So there is some lab evidence that vitamin
D may be anti-cancer," Klein said.
It could be that the risk comes
from too little vitamin D, and that consuming lots of vitamin
D is not helpful, doctors say.
How much should people get? The
recommended daily amount is 400 international units, but most
scientists think that is probably low, Li said.
Most milk is fortified with vitamin
D, but drinking a lot of it might raise the risk of prostate cancer
because of its calcium content. Getting enough vitamin D from
food is difficult, but doctors do not recommend supplements because
they can cause unsafe levels of calcium to build up.
"If you start overloading on vitamin
D you're going to cause other problems," said Dr. Durado Brooks,
chief of prostate cancer research at the American Cancer Society.
Hence the advice to get a little
sunlight but not too much, because that can raise the risk
of skin cancer.
Researchers presented two other
studies from the same group of 15,000 doctors. One found that
men who were overweight were 30 percent more likely to die of
prostate cancer than normal-weight men. Those who were obese were
nearly twice as likely to die.
The second study examined a protein
in the blood, acid-labile subunit or ALS, that blocks the effects
of a hormone that spurs cells to grow and has been linked to many
types of cancer.
Compared with men with low levels
of ALS, men with higher amounts of it were 40 percent to 60 percent
more likely to develop prostate cancer, and their chances of having
advanced cancer more than doubled, said Lorelei Mucci, a Harvard
epidemiologist who led the study.
ALS needs more study, but may be
a new marker for predicting cancer risk and may be a target for
developing new treatments, Klein said.
Reference Source 102
February 21, 2005